Relationships among ecological traits of wild bee communities along gradients of habitat amount and fragmentation

Abstract

Amount of semi‐natural habitats (permanent grasslands, woodlands and hedgerows) and their level of fragmentation are among the main determinants of wild bee diversity in agricultural landscapes. However, their impact on the distribution of bee ecological traits has received little attention. In this study, we aimed to explore whether changes in the distribution of bee ecological traits along gradients of habitat amount and fragmentation were due to a direct effect of landscape context on multiple traits (‘response traits’) or to a correlation of response traits with other ecological traits not involved in the response of bee species to landscape context. In two study regions in southwest France and southeast Australia, we used a RLQ analysis (three‐table ordination method) to link bee traits with habitat amount and fragment isolation measured at the landscape scale. We found that bee ecological traits shifted at the community‐level in association with landscape gradients, whereas species‐level associations among bee traits and phylogenetic clustering in bee communities were of only minor importance in determining such shifts. We found that traits such as body size and nest location were closely linked to habitat amount and fragmentation. We also observed regionally‐specific relationships among ecological traits, suggesting that the regional species pool can play an important role in determining the response of bee communities to habitat amount and fragmentation. Our findings suggest that improved knowledge about how trait‐based responses mediate the impact of landscapes on wild bee communities will allow better prediction and understanding of subsequent effects on ecosystem functioning.

On the inconsistency of pollinator species traits for predicting either response to land‐use change or functional contribution

“…Despite some generalities that emerge across taxa, with rare species, big species, specialists, and higher trophic levels being in general more sensitive to disturbances (Fisher and Owens ), there is a large variation in the response of the species with those traits (Fritz et al , Sguin et al 2014). Work specifically on native bees has found that traits such as specialization, body size, and sociality may predict responses to land use (Winfree et al , Bommarco et al , Williams et al , Bartomeus et al , Hopfenmüller et al , Rader et al , De Palma et al , Kremen and M'Gonigle , Carrié et al ). However, studies often find contrasting results.…”

Connecting models, data, and concepts to understand fragmentation's ecosystem‐wide effects

“…Mitchell et al () found that forest fragment isolation and distance from forest fragment edges affected multiple services, including those above (herbivory, productivity) and below (P, N, C) ground. Carrié et al () provide a detailed cross‐ecosystem analysis of how habitat fragmentation affects changes in the response and effect traits in wild bee communities, and thereby indirectly a critical ecosystem service, crop pollination. Understanding the effects of fragmentation on ecosystem services has been limited within the long‐term experiments, as they were not created to test these responses.…”

“…Observations in particular can be used to examine a variety of landscape contexts, especially at large spatial scales not attainable with experiments. Our Special Issue highlights some of the benefits of observational studies for advancing our understanding of fragmentation, including the use of observational studies to test hypotheses regarding conceptual models of habitat fragmentation (Brudvig et al ), responses in fragmented agricultural landscapes (Carrié et al ), models comparing patch‐matrix with mosaic approaches (Leroux et al ), and ecological responses in fragments created by people centuries ago (Reynolds et al ). Our feature articles are followed in this same issue of Ecography by a number of others that accomplish objectives not possible in controlled experiments, for example understanding fragmentation's effects over large geographic regions within continents.…”

Spectro-Temporal Heterogeneity Measures from Dense High Spatial Resolution Satellite Image Time Series: Application to Grassland Species Diversity Estimation

“…Grasslands are mainly located on steep slopes, whereas annual crops are in the valleys on the most productive lands. The climate is sub-Atlantic with sub-Mediterranean and mountain influences (mean annual temperature, 12.5 • C; mean annual precipitation, 750 mm) [27,28]. …”